1. Integumentary System

2. Skin as an Organ Largest organ in human body All adults have 20-25 lbs of skin 4 Functions- Skin as radiator

3. Integumentary Structures Components of the Integumentary System Figure 5-1

4. Quick Overview Epidermis Tissue= Stratified Squamous No blood vessels in this layer Dead Skin Cells Dermis Tissue=Dense Irregular Collagenous Connective Active area of skin Hypodermis (not actually skin) Tissue=Areolar & Adipose Connects skin to body (Epi=On, On the surface of something) (Hypo=Below, Less than)

5. 4 Major Structures in Dermis 1.Hair Follicles- All anchored in dermis Aid in temp regulation by trapping air to help insulate. Sensitive-Can sense vibrations 2. Glands Sweat Glands-Evaporation cools you Oil Glands-Keep dead skin cells together. Protects from things getting in. (sebaceous gland)

6. 4 Major Structures in Dermis 3. Blood Vessels Bring nutrients and fluids to cells. Bleed when you cut into dermis (not epidermis). 4. Sensory Nerves Sense Temperature Pain Touch (Meisners Corpuscle-Light Touch; Pacinian Corpuscle-Deep pressure)

7. Hypodermis Link Between Body & Skin Find adipose mixed in with areolar tissue Most fat in your body is directly under skin. Major blood vessels

8. Dermis Boundary between dermis & epidermis isn’t flat to prevent slipping apart. Dermal Papilla-Bumps in dermis Blisters caused by intense, prolonged friction. Epidermis separates from dermis and fluid enters. Any change to dermis will be seen through epidermis (scars, surface contours, etc) Scars are in dermis Causes Fingerprints Dermal Papilla

9. Blisters

10. Epidermis Super thin Stratified Squamous 5 Layers – Stratum Corneum – Stratum Lucidum (Only Soles of Feet & Palms) – Stratum Granulosum – Stratum Spinosum – Stratum Basale Living Layers!

11. Started from the bottom now we’re here..Stratum Basale (hehehe) All other cells come from here #1 Job is Reproduction- Cells born here aren’t in full production mode yet, they don’t grow up here.

12. Stratum Basale (cont) 2 Main types of cells in Stratum Basale – mostly Keratinocytes: Make protein- keratin to give epithelium strength. Don’t produce keratin yet in basale layer. – Melanocytes: Make pigment melanin (colors your skin). More Melanin=darker skin. Albinism=Malfunctioning melanocytes

13. Stratum Spinosum Cells from basale go here. Cells here are growing up and producing keratin, etc. Like teenagers.

14. Stratum Spinosum (cont) Melanocytes don’t reproduce in numbers. When they do=melanoma (malignant skin cancer)malignant skin cancer Melanin-natural sunblock – Absorbs UV Rays, blocks UV rays from damaging dermis. – Tanning occurs by UV radiation stimulating excess melanin production.

15. Stratum Granulosum Old cells Been producing keratin for so long, we can see keratin “GRANULES” Not much moisture/nutrient s Cells on the verge of death.

16. Stratum Corneum Top layer Dead skin cells Still tough because of protein keratin.

17. Stratum Lucidum Palms/Soles of Feet Less melanocytes, decreased pigment Change from granulosum before corneum to thicken.

18. Sebaceous Glands (oil glands) Occur over entire body - Except palms and soles Simple alveolar glands –Holocrine secretion – entire cell breaks up to form secretion –Secretes an oily substance called sebum –Most are associated with a hair follicle Functions of sebum –Softens and lubricates hair and skin –Skin waterproofing –Collects dirt

19. Sweat (Sudoriferous) Glands Two types: Eccrine (Merocrine) –Most abundant sweat gland –“True sweat” 99% water with some salts Contains traces of metabolic wastes ~ 2% urea –Role in thermoregulation –Widely present in skin (up to 500/cm 2 ) Apocrine –Odorous secretion –Absent before puberty –Present in axillary, areolar, anal and genital areas

20. Eccrine (Merocrine) Gland Figure 5.10b

21. Nails Scalelike modification of epidermis made of hard keratin Parts of the nail –Free edge –Body - d ense mass of keratinized cells –Root –Nail folds –Eponychium – cuticle

22. Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response. Epidermis Dermis After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulation in the area. Clotting around the edges of the affected area partially isolates the region. Sweat gland Scab Macrophages and fibroblasts Migratory epithelial cells Granulation tissue Skin Injury and Repair

23. One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating. Fibroblasts After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis. Scar tissue Skin Injury and Repair

24. Table 5-1

25. Aging of the Skin Major Age-Related Changes –Injury and infection increase –Immune cells decrease –Sun protection diminishes –Skin becomes dry, scaly –Hair thins, grays –Sagging, wrinkles occur –Heat loss decreases –Repair slows

26. Effects of UV Radiation Beneficial effect - activates synthesis of vitamin D 3 Harmful effects –Sun burn –Wrinkles, premature aging –Malignant melanoma –Basal cell carcinoma

27. Types and Growth of Hair Vellus hairs –Body hairs of women and children Terminal hairs –Hair of scalp –Axillary and pubic area (at puberty) Hair thinning and baldness –Due to aging –Male pattern baldness

28. Burns Classified by severity –First-degree burn – only upper epidermis is damaged –Second-degree burn – upper part of dermis is also damaged Blisters appear Skin heals with little scarring –Third-degree burn Consume thickness of skin Burned area appears white, red, or blackened

29. Burns First-degree (epidermis only; redness) Second-degree (epidermis and dermis, with blistering) Third-degree (full thickness, destroying epidermis, dermis, often part of hypodermis)

30. Estimating Burns Using the Rule of Nines Figure 5.11a

31. Skin Cancer Basal cell carcinoma –Least malignant and most common Squamous cell carcinoma –Arises from keratinocytes of stratum spinosum Melanoma –A cancer of melanocytes –The most dangerous type of skin cancer

32. Skin Cancer Squamous cell carcinoma Figure 5.12 Melanoma Squamous cell carcinoma Basal cell carcinoma

33. The Skin Throughout Life Epidermis –Develops from embryonic ectoderm Dermis and hypodermis –Develop from mesoderm Melanocytes –Develop from neural crest cells

34. The Skin Throughout Life Fetal skin –Well formed after the fourth month –At 5-6 months The fetus is covered with lanugo (downy hairs) –Fetal sebaceous glands produce vernix caseosa